Novel synthesis strategies based on the geometrical and topological principles outlined here open up pathways to a new class of spherical clusters with icosahedral symmetry of the type (pentagon)(12)(linker)(30)- also called keplerates -where the centers of the 12 pentagons span an icosahedron and the centers of the 30 linkers an icosidodecahedron. Remarkably, sizing of a spherical molecule is possible for the first time. In addition to their large size of several nanometers, these molecules show unusually high symmetries. When large numbers of paramagnetic metal centers like 30 Fe-III or 20 VO2+ are integrated within their structure, extraordinary spin topologies can be realized on a discrete molecular level. Further functionalization of these systems allows, e.g. to link them forming chains or layers in solid state reactions at room temperature. (C) 2001 Elsevier Science B.V. All rights reserved.